(a) Field
The subject matter disclosed generally relates to a method for extracting anthocyanin derivatives. More particularly, the subject matter generally relates to a method for extracting anthocyanin derivatives from a plant source such as blueberries.
(b) Related Prior Art
Anthocyanins are water-soluble vacuolar pigments that may appear red, purple, or blue according to their pH. They belong to a parent class of molecules called flavonoids synthesized via the phenylpropanoid pathway. They are odorless and nearly flavorless, contributing to taste as a moderately astringent sensation. Anthocyanins occur in all tissues of higher plants, including leaves, stems, roots, flowers, and fruits. Anthocyanins are derivatives of anthocyanidins which include pendant sugars.
In flowers, bright reds and purples are adaptive for attracting pollinators. In fruits, the colorful skins also attract the attention of animals, which may eat the fruits and disperse the seeds. In photosynthetic tissues (such as leaves and sometimes stems), anthocyanins have been shown to act as a “sunscreen”, protecting cells from high-light damage by absorbing blue-green and UV light, thereby protecting the tissues from photoinhibition, or high-light stress. This has been shown to occur in red juvenile leaves, autumn leaves, and broad-leaved evergreen leaves that turn red during the winter. It has also been proposed that red coloration of leaves may camouflage leaves from herbivores blind to red wavelengths, or signal unpalatability, since anthocyanin synthesis often coincides with synthesis of unpalatable phenolic compounds.
In addition to their role as light-attenuators, anthocyanins also act as powerful antioxidants. However, it is not clear as to whether anthocyanins can significantly contribute to scavenging of free-radicals produced through metabolic processes in leaves, since they are located in the vacuole and, thus, spatially separated from metabolic reactive oxygen species. Some studies have shown that hydrogen peroxide produced in other organelles can be neutralized by vacuolar anthocyanin.
Anthocyanins are found in the cell vacuole, mostly in flowers and fruits but also in leaves, stems, and roots. In these parts, they are found predominantly in outer cell layers such as the epidermis and peripheral mesophyll cells.
Most frequent in nature are the glycosides of cyanidin, delphinidin, malvidin, pelargonidin, peonidin, and petunidin. Roughly 2% of all hydrocarbons fixated in photosynthesis are converted into flavonoids and their derivatives such as the anthocyanins. There is no less than 109 tons of anthocyanins produced in nature per year. Not all land plants contain anthocyanin; in the Caryophyllales (including cactus, beets, and amaranth), they are replaced by betalains. However, anthocyanins and betalains have never been found in the same plant.
Plants rich in anthocyanins are Vaccinium species, such as blueberry, cranberry and bilberry, Rubus berries including black raspberry, red raspberry and blackberry, blackcurrant, cherry, eggplant peel, black rice, Concord grape and muscadine grape, red cabbage, and violet petals. Anthocyanins are less abundant in banana, asparagus, pea, fennel, pear, and potato, and may be totally absent in certain cultivars of green gooseberries.
Nature, primitive agriculture, and plant breeding have produced various uncommon crops containing anthocyanins, including blue- or red-flesh potatoes and purple or red broccoli, cabbage, cauliflower, carrots, and corn. Tomatoes have been bred conventionally for high anthocyanin content by crossing wild relatives with the common tomato to transfer a gene called the anthocyanin fruit tomato (“aft”) gene into a larger and more palatable fruit.
Tomatoes have also been genetically modified with transcription factors from snapdragons to produce high levels of anthocyanins in the fruits. Anthocyanins can also be found in naturally ripened olives, and are partly responsible for the red and purple colors of some olives.
Anthocyanins are considered secondary metabolites as a food additive with E number E163 (INS number 163); they are approved for use as a food additive in the EU, Australia and New Zealand.
Richly concentrated as pigments in berries, anthocyanins were the topics of research presented at a 2007 symposium on health benefits that may result from berry consumption. Laboratory-based evidence was provided for potential health effects against: cancer; aging and neurological diseases; inflammation; diabetes; and bacterial infections.
Cancer research on anthocyanins is the most advanced, where black raspberry (Rubus occidentalis L.) preparations were first used to inhibit chemically induced cancer of the rat esophagus by 30-60% and of the colon by up to 80%. Effective at both the initiation and promotion/progression stages of tumor development, black raspberries are a practical research tool and a promising therapeutic source, as they contain the richest contents of anthocyanins among native North American Rubus berries.
Work on laboratory cancer models has shown that black raspberry anthocyanins inhibit promotion and progression of tumor cells by: stalling growth of pre-malignant cells; accelerating the rate of cell turnover, called apoptosis, effectively making the cancer cells die faster; reducing inflammatory mediators that initiate tumor onset; inhibiting growth of new blood vessels that nourish tumors, a process called angiogenesis; and minimizing cancer-induced DNA damage.
On a molecular level, berry anthocyanins were shown to turn off genes involved with proliferation, inflammation and angiogenesis, while switching on apoptosis.
In 2007, black raspberry studies entered the next pivotal level of research—the human clinical trial—for which several approved studies are underway to examine anti-cancer effects of black raspberries and cranberries on tumors in the esophagus, prostate and colon. A growing body of evidence suggests that anthocyanins and anthocyanidins may possess analgesic properties in addition to neuroprotective and anti-inflammatory activities.
Many methods have been studied in the past to obtain anthocyanin derivatives. Some known methods of anthocyanin extraction to obtain high extraction yields in terms of weight of recovered anthocyanin compared to weight of anthocyanin present in the source matter. However, those methods generally do not provide an optimal control on the purity level of the anthocyanin extracts obtained.
There is therefore a need to provide an improved method for extracting and purifying anthocyanin derivatives, and more particularly, there is a need to provide an improved method for extracting and purifying anthocyanin derivatives from a plant source such as blueberries.